Anderson ft al

ABSTRACT

TO FACILITATE STARTING, AN INTERNAL COMBUSTION ENGINE IS PROVIDED WITH A DECOMPRESSION PORT LOCATED AT A SELECTED DISTANCE FROM THE TOP OF THE CYLINDER SO AS TO DECREASE COMPRESSION DURING CRANKING OF THE ENGINE. THE PORT IS CONTROLLED BY A VALVE WHICH IS NORMALLY CLOSED AND WHICH PREFERABLY COMPRISES A BALL SHAPED VALVED MEMBER PRESSED AGAINST AN ANNULAR VALVE SEAT. A UNITARY LOCKING ELEMENT HOLDS THE ENGINE THROTTLE CONTROL MEMBER IS SELECTED POSITION FOR STARTING AND ALSO HOLDS THE DECOMPOSITION VALVE OPEN. AS SOON AS THE ENGINE STARTS, ACTUATION OF THE THEREBY RESULTS IN THE AUTOMATIC CLOSING OF THE DECOMPRESSION VALVE.

June 27, 1972 ANDERSON ETAL e- 2 ,410

DECOMPRESSION CONTROL FOR INTERNAL COMBUSTION ENGINE Original Filed July19, 19s? Zfa .nlllll United States Patent Ofice Re. 27,410 Reissued June27, 1972 27,410 DECOMPRESSION CONTROL FOR INTERNAL COMBUSTION ENGINEAlbert E. Anderson, Greenwich, Albert K. Newman,

Noroton, Chris Schou, Greenwich, and James A. Ransom, Bryam, Conn., andWalter Gorski, Armonk, N.Y., assignors to Textron Inc.

Original No. 3,418,992, dated Dec. 31, 1968, Ser. No. 654,446, July 19,1967. Application for reissue Dec. 23, 1970, Ser. No. 100,963

Int. Cl. F011 13/08 US. Cl. 123-182 12 Claims Matter enclosed in heavybrackets I: appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OF THE DISCLOSURE To facilitate starting, an internalcombustion engine is provided with a decompression port located at aselected distance from the top of the cylinder so as to decreasecompression during cranking of the engine. The port is controlled by avalve which is normally closed and which preferably comprises a ballshaped valve member pressed against an annular valve seat. A unitarylocking element holds the engine throttle control member in selectedposition for starting and also holds the decompression valve open. Assoon as the engine starts, actuation of the throttle control memberreleases the locking element and thereby results in the automaticclosing of the decompression valve.

The present invention relates to internal combustion engines andparticularly to means for facilitating the starting of such engines. Theinvention is particularly applicable to small 2-cycle engines of thekind used for chain saws and other portable tools, lawn mowers,o-utboard motors, etc.

In order to increase the horsepower rating and efficiency of smallinternal combustion engines while keeping the weight of the engines at aminimum, it is desirable to operate the engines at a high compressionratio. The resistance offered by this high compression makes itdiflicult to turn the engines over during cranking.

In order to facilitate the starting of internal combustion engines, ithas heretofore been proposed to provide means for relieving, at least inpart, the compression in the engine cylinder during cranking.Compression is relieved by means of a port in the engine cylinderpermitting the exhaust of gases from the cylinder during at least a partof the compression stroke. The decompression port must, of course, beclosed during normal operation of the engine as it would otherwiseresult in an objectionable loss of power and efficiency. Accordingly,the port is provided with valve means which is opened during cranking ofthe engine and must be closed after the engine has started.

While a decompression valve makes it easier to crank an internalcombustion engine, it is disadvantageous in that it requires theoperator to actuate an additional control device. This isparticularlyobjectionable in handheld power tools such as chain saws.The operator is required to hold the tool with one hand-preferablyresting it on a supporting surface-while pulling the starter cable withthe other hand. The addition of an extra control requiring the operatorsattention complicates the starting procedure.

It is an object of the present invention to provide a unitary controlsystem by which a decompression valve is automatically held in an openposition during cranking of the engine and is automatically closed whenthe engine has started. The operator performs only those functions whichhe customarily performs in starting the engine. No additional action isrequired of the operator to effect a reduction in compression duringcranking of the engine and re-establishing full compression after theengine has started.

When the engine is running, it is important to maintain thedecompression valve tightly closed in order to avoid leakage of gaseseither during the compression stroke or the firing stroke of the engine.It has been found that with decompression valves of former design, it isdifficult consistently to avoid leakage. It is accordingly a furtherfeature of the invention to provide an improved decompression valvewhich is of simple construction, yet is highly effective in maintaininga fluid tight seal despite the high pressures to which the valve issubjected during operation of the engine.

The invention is applicable to engines provided with hand starting,e..g., by means of the usual pull cord. With hand starting, thedecompression system in accordance with the invention materially reducesthe effort required for cranking the engine. The invention is alsoadvantageous when applied to engines provided with self starters in thatthe reduced effort required for cranking the engine makes it possible touse smaller, lighter and less expensive starters.

The invention will be more fully understood from the followingdescription of preferred embodiments illustrated by way of example inthe accompanying drawings in which:

FIG. l is a fragmentary perspective view illustrating application of theinvention to an internal combustion engine,

FIG. 2 is a side view with portions broken away to show internalconstruction,

FIG. 3 is a view taken partly in section approximately on the line 3-3in FIG. 2 with portions broken away to show the construction of thedecompression valve,

FIG. 4 is an enlargement of a portion of FIG. 3, and

FIGS. 5 and 6 are views corresponding to a portion of FIG. 3 but showingdifferent valve constructions.

In the drawings, there is shown a portion of an internal combustionengine 1 which, by way of example, may be a single cylinder, Z-cycleengine. The engine 1 is illustrated as having a cylinder 2 in which apiston 3: is reciprocable. A spark plug 4 provided in the cylinder headis connected by an insulated wire 5 to a magneto or other source ofelectricity.

The engine 1 is shown providing with a hollow grip or handle portion 7with which is associated a member 8 for controlling the speed of theengine, e..g., by regulating the supply of fuel to the engine cylinder.The engine control member 8 is shown in the form of a trigger which isapproximately L-shaped as seen from the side (FIG. 2) and is swingableabout a pivot pin 9 which projects laterally inside the hollow handle 7.The trigger 8 is connected to the carburetor or other fuel supply means(not shown) of the engine in such manner that the fuel supply,

nd hence engine speed, is increased when the trigger 8 swung about itspivot 9 in a clockwise direction as iewed in FIG. 2. A spring 10 acts onthe trigger 8 to ving it in a counter-clockwise direction to a positionin hich only sufiicient fuel is supplied to the engine for it run atidling speed.

In order to reduce the force required for cranking the ngine to startit, the engine cylinder 2 is provided with decompression port 12 whichis located in the cylinder all at a selected distance from the head ofthe cylinder. he location of the decompression port is selected so aspermit the escape of a portion of the fuel-air charge I the cylinderduring the compression stroke while prolding compression of theremaining portion of the charge Eter the top of the piston passes thedecompression port. y way of example, the decompression port is spacedour the head of the cylinder a distance equal to aproximately to percentof the stroke of the piston. his location has been found to reduce to anacceptable alue the force required for cranking the engine while illretaining sufficient charge and compression for reliale firing of theengine.

The decompression port 12 is controlled by a valve 14 that the port isopen to provide decompression during :arting but is tightly closed atother times to prevent :akage of gas from the cylinder when the engineis runing. The decompression control valve 14 is shown as :mprising avalve housing 15 which is screwed or otherise secured in a boss 16provided on the cylinder wall. .t its inner end, the valve housing 15 isprovided with an pening which is aligned with the decompression port 12l the cylinder wall and is surrounded by an annular alve seat 17. Thevalve seat is preferably of conical rape with an angle of inclinationof, e.g., about 45 FIG. 4)-. The valve housing 15 is hollow with acylinrical bore 18 which is aligned with the decompression ort 12 but oflarger diameter. A discharge port 19 opens irough the side wall of thehousing at a location just utwardly of the valve seat 17. The bore ofthe valve ousing receives a plunger 21 which is longitudinally slidblein the bore. A valve member 22, shown in the form of spherical ball, isreceived in the bore between the valve :at 17 and the inner end of theplunger 21. The ball 22 i of hard corrosion resistant material, e.g.,stainless steel, [id is of a diameter which is less than that of thebore 8 but greater than the minimum diameter of the valve :at so as toengage the seat as illustrated in FIG. 4. A pring 23 supported on afixed stud 24 engages in a groove 1 the outer end of the plunger 21 andacts to press the lunger inwardly against the ball 22 and thereby press1e ball into tight engagement with the valve seat 17 to lose thedecompression port 12.

In accordance with the invention, unitary control means provided forholding the fuel member 8 in proper posion for starting andsimultaneously holding the decomression valve 14 in open position. Asillustrated by way i example in the drawings, the control meanscomprises )cking means for releasably locking the fuel control iember 8in selected position and connections between 1e locking means and thedecompression valve 14 to old the valve open against the action of thespring 23 hen the locking means is in locked position. The locking teamsis shown in the form of a push-button 25 having head portion 26 and astem portion 27 which is slidable 1 a bushing 28 extending through ahole in one side all of the hollow hand grip portion 7. At its innerend, 1e stem 27 is provided with a reduced portion terminatlg in a head29 of approximately the same cross sectionl dimensions as the stem. Acoil spring 31 surrounding 1e stem 27 acts between the side wall of thehand grip ortion 7 and the head 26 to bias the push-button to an uterposition as shown in solid lines in FIG. 3.

The locking element 25 is so located and proportioned 1at when the fuelcontrol member 8 is moved to a posi- .on to provide the desired amountof fuel for starting the Cit engine and whenv the push-button 25 ispushed inwardly against the action of spring 31 to the position shown indotted lines in FIG. 3, the head portion 29 at the inner end of the stem27 engages a web portion 32 on the fuel control member 8 so as to holdthe push-button in its inner position and thereby hold the fuel controlmember 8 in engine starting position.

The locking element 25 is suitably connected to the plunger 21 of thedecompression valve 14 so as to hold the plunger out against the forceof spring 23 and thereby hold the valve in open position when thelocking element is in locked position as indicated by bro-ken lines inFIG. 3. In the example illustrated in the drawings, the connection is bymeans of a lever 35 having an intermediate portion which is rotatablysupported by a bracket 36 secured to a stationary portion of the engine,e.g., by screws 37. An arm 35a at one end of the lever 35 extends into ahole 38 provided in the plunger 21 near its outer end. An arm 35b at theother end of the lever 35 extends into an opening 29a in the headportion 26 of the locking elemtnt 25. The shape and location of thelever 35 are such that when the locking element 25 is pushed inwardly toits locked position as shown in broken lines in FIG. 3, the lever isrotated in the bearing provided by bracket 36 so as to swing the arm 35ain a counter-clockwise direction as seen in FIG. 3 and thereby move theplunger 21 outwardly against the bias of its spring 23. The valve member22 is thereby released from its seat 17 to open the valve. The effectivelength of the lever arm- 35b is greater than that of arm 35a to providea mechanical advantage valve without requiring excessive pressure on thepush button 25.

In preparation for starting the engine, the operator grasps the handle 7and, with his middle finger, applies pressure to the trigger 8 to swingit about its pivot 9 in a clockwise direction as viewed in FIG. 2. Withhis forefinger, he then pushes the locking element 25 to its innerposition and then releases the trigger 8 which, under pressure of thespring 10, returns toward idle position until the web portion 32 engagesthe reduced portion of the stem 27 of the locking element 25. Engagementof the head portion 29 on the inner end of stem 27 with the web portion32 of the trigger 8 retains the locking element 25 in locked positionand thereby holds the trigger 8 in position to supply the proper amountof fuel for starting. Movement of the locking element 25 to lockedposition has simultaneously opened the decompression valve 14 by reasonof the connections provided by the lever 35. The engine is then readyfor starting and is suitably cranked either by hand or by a starter. Assoon as the engine starts, the operator applies pressure to the trigger8 to regulate the speed of the engine as desired. The web portion 32 ofthe trigger 8 is thereby disengaged from the head 29 at the inner end ofstem 27 of the locking element so that the locking element is moved byits spring 31 to its outer position as shown in solid lines in FIG. 3.By reason of the interconnection provided by lever 35, this movement ofthe locking element 25 releases the plunger 21 of the decompressionvalve 14 so that the plunger is moved inwardly by its spring 23 to pressthe ball 22 against the valve seat 17 and thereby close thedecompression port 12.

When the decompression valve is held open by the lever 35 duringstarting of the engine, a portion of the fuel-air charge is releasedthrough the decompression port 12 and discharge port 19 during a portionof each compression stroke. The exhaust port 19 of the decompressionvalve 14 may, if desired, be connected to the crank case of the engineso as to return the discharge fuel-air charge to the crank case.Alternatively, the discharge port 19 may be connected to the exhaustsystem of the engine. However, in practice it has been found that theamount of fuel-air mixture discharged through the decompression portduring starting of the engine is so small that it can be dischargeddirectly to the atmosphere without any objectionable effects.

The ball 22 which constitutes the valve member of the decompressionvalve 14 is self-centering and is also free to rotatewhen not beingpressed by the plunger 21. Presumably by reason of such rotatability ofthe ball, the valve has been found to be self-cleaning so as to assuregas tight closure of the decompression port at all times when the valve14 is closed. Objectionable leakage of gas from the cylinder is therebyavoided.

While it has been found in practice that gas pressure inside thecylinder is sufiicient to unseat the ball 22 when the plunger 21 iswithdrawn by the lever 3-5, means can be provided if desired forpositively withdrawing the ball from its seat when the plunger 21 ismoved outwardly. Such an arrangement is illustrated by way of example inFIG. 5 in which the plunger 21 is shown provided at its inner end withportions 40 which extend past the midpoint of the ball and arerestricted so as to cage the ball while leaving it free to rotate andfree to move laterally sufiiciently to be self-centering.

Another form of the decompression valve is illustrated in FIG. 6. Avalve plunger 41 corresponding to the plunger 21 illustrated in FIGS. 1to 5 is divided into two portions namely, an outer portion 41a and aninner portion 41b which constitutes a valve member. The outer portion41a is provided with an opening 42 to receive the arm 35a of the lever35 and with a transverse groove to receive a spring 23. The innerportion 41b of the plunger is rotatable relative to the outer portion41a. Hence, although the outer portion is held against rotation by thelever arm 35a and spring 23, the inner portion 41b is free to rotate.The two portions of plunger 41 are shown rotatably connected with oneanother by a reduced portion 43 on the inner end of the outer plungerportion 41a fitting sufiiciently freely in a corresponding recessprovided in the outer end of the inner plunger portion 41b to permitfree rotation. The inner plunger portion 41b has a reduced portion 44 ofsmaller diameter than the inner diameter of the bore 18 of the valvehousing. At its inner end, the inner plunger portion 41b has afrustoconical portion 45 adapted to seat on the valve seat 17 and a tipportion 46 adapted to project into the decompression port 12 to keep itclear of carbon or other deposits. It has been found that by reason ofthe rotatability of the inner plunger portion 41b constituting a valvemember, the valve is self-adjusting and self-cleaning so as to maintaina fluid tight seal when the valve is in closed position.

While preferred embodiments of the invention have been illustrated byway of example in the drawings and have been herein particularlydescribed, it will be understood that the invention is not therebylimited to the particular examples shown.

What We claim is:

1. Control means for an internal combustion engine having a cylinder anda hand grip, said control means comprising a decompression port in saidcylinder, a normally closed compression relief valve closing said port,an engine fuel control member associated with said hand grip andoperable to control the supply of fuel to said engine, locking means forreleasably locking said fuel control member in selected position forstarting said engine, said locking means being movable between a lockingposition and a released position and. means connecting said lockingmeans with said valve to hold said valve in open position when saidlocking means is in looking position.

2. Control means according to claim 1, in which said compression reliefvalve comprises a valve seat, a ballshaped valve member adapted to seaton said seat and spring pressed means normally pressing said valvemember on its seat.

3. Control means according to claim 2, in which said spring pressedmeans comprises a longitudinally slidable plunger and spring meanspressing said plunger toward said valve member.

4. Control means according to claim 3, in which said valve membercomprises a ball rotatably secured to an end of said plunger.

5. Control means according to claim 1, in which said locking meanscomprises a movable plunger and spring means urging said plunger towardreleased position, said plunger and fuel control member havingcooperating latch means for holding said plunger in locking position,said latch means being releasable by movement of said fuel controlmember in a direction to increase engine speed.

6. Control means according to claim 1, in which said compression releasevalve comprises a valve seat, a rotatable valve member adapted to seaton said seat and spring pressed means normally pressing said valvemember onto its seat.

7. Control means according to claim 1, in which said compression releasevalve comprises a valve seat, a valve housing having a bore aligned withsaid seat and a plunger longitudinally movable in said bore, saidplunger comprising an outer non-rotating portion and an inner rotatableportion having a valve surface adapted to seat on said seat.

[8. Unitary control means for an internal combustion engine having acylinder with a side wall and a head and a piston reciprocable in saidcylinder, said control means comprising a manually operable startingcontrol member which controls a starting function of the engine and ismovable between a starting position for starting the engine and arunning position when the engine has been started and is running, adecompression port located in the side wall of the cylinder and spacedfrom the. head of the cylinder a distance equal to about 15% to 25% ofthe stroke of the piston, a normally closed compression relief valve forclosing said port, and means connecting said starting control memberwith said valve to hold said valve in open position when said startingcontrol member is in starting position] 9. Control means according toclaim [8] 11, in which said compression relief valve comprises anannular valve seat surrounding said port, a rotatable self-centeringvalve member seating on said seat to close said port and movableoutwardly from said seat to open said port and in which said firstbiasing means comprises spring means biasing said valve member to closedposition.

10. Control means according to claim 9, in which said valve member has aportion adapted to project into said decompression port to keep it clearof engine deposits.

11. In a hand held power tool comprising an internal combustion enginehaving a cylinder with a side wall and a head and a piston reciprocablein said cylinder, and provided with a hand grip, unitary control meanscomprising a decompression port located in the side wall of the cylinderand spaced from the head of the cylinder a distance equal to about 15%to 25 of the stroke of the piston, a movable compression relief valvefor closing said port, first biasing means for biasing said valve toclosed position, a manually operable fuel control member associated withsaid hand grip and operable to control the supply of fuel to the engineand thereby control engine speed, second biasing means for biasing saidfuel control member to a position in which only sufiicient fuel issupplied to the engine for it to run at idling speed, locking means forreleasably holding said fuel control member in a selected position forstarting said engine, said locking means being movable between a lockingposition in which said locking means hold said fuel control member inengine-starting position and a released position in which said fuelcontrol member is released by said locking means, and means connectingsaid locking means with said compression relief valve to hold said valvein open position when said locking means is in locking position and torelease said compression relief valve for positioning it i closedposition by said first biasing means when said )cking means is inreleased position.

12. Control means according to claim 11, in which said annecting meanscomprises lever means providing a mehanical advantage whereby themovement of said locking leans between released and locking position isgreater ran the movement of said valve between closed and open osition.

13. Control means according to claim 11, in which said raking meanscomprises a movable locking member and wring means biasing said lockingmember toward said zleased position, said locking member and said fuelcon- '0[ member having interengaging portions for releasably ztainingsaid locking member in locking position when zid fuel control member isin engine-starting position, zid portions being disengaged by movementof said fuel ontrol member in a direction to increase engine speed tozlease said locking member for movement to released osition by saidspring means.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

UNITED STATES PATENTS 521,443 6/1894 Shepperd 123-182 2,440,483 4/19'48Mennesson 123182 2,625,924 1/ 19 53 Friedlob 123-182 2,742,380 4/1956Peters 123-182 2,778,349 1/19-57 Thommen 123182 2,922,436 1/1960 Brash123-182 X 2,947,300 8/1960 Trapp 123182 FOREIGN PATENTS 1,013,426 1/1958Germany 123-482 WENDELL E. BURNS, Primary Examiner

